This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This research seeks to develop and validate a novel set of dietary biomarkers based on naturally-occurring isotopic differences among foods. Isotopic differences can distinguish foods from marine and terrestrial sources, foods grown at high and low latitude, and foods based on corn or sugar cane. Because Yup'ik Eskimos rely on a mix of subsistence and US market foods, they present an ideal population for testing these biomarkers of intake. First, we will test whether the isotopic signatures of key foods can be used to define nutritionally-relevant food groups, by collecting and analyzing multiple isotope signatures of commonly consumed foods. Secondly, we will enroll 100 individuals in an age and sex stratified design and compare intake measured by repeated diet records and by the isotope signatures of red blood cells, hair, and fingernails. Finally, we will test whether isotopic measurements of hair can detect dietary change, by revisiting 50 participants in a different season and collecting a second set of diet records and hair samples. Preliminary data collection reveals strong isotopic differences between subsistence and non subsistence Yup'ik foods. Enrollment of research participants is nearing completion, and preliminary data analyses are underway. Yup'ik Eskimos exhibit low levels of chronic, obesity-related disease, despite having relatively high rates of obesity. Understanding how the unique diet of Yup'ik Eskimos either protects or predisposes them to disease requires practical biomarkers of diet pattern. This approach to diet assessment will be developed specifically for use in underserved Yup'ik Eskimo communities, although the method will be adaptable to other populations. There are no expected changes in the gender/minority composition of research subjects for this project.